A bidirectional drive for the hands of a watch with the aid of a stepping motor has already been proposed. U.S. Pat. No. 4,112,671 describes a single-phase stepping motor with two directions of rotation. Control of the rotation in one direction or the other takes place by means of an electronic circuit which supplies pulses of different shapes. The main drawback of this type of drive is the narrow range of operation of the motor as regards voltage. If the rated voltage is not kept to, the steps are no longer ensured, especially for counterclockwise operation.
French Published Application No. 79 22276 discloses a two-phase stepping motor comprising a two-pole rotor and two coils, each disposed at an angle to a symmetry axis in order to subject spatially phase-shifted magnetic fields to the rotor. Although this motor offers reliable operation in both directions of rotation, its output is relatively low. The output of a micromotor depends, for one thing, on its coil volume, usually small owing to design imperatives, and for another thing, on the flux created by the magnet and coupled with the coil. The arrangement of the pole pieces in this motor means a passage surface of the magnetic flux limited to the thickness of the stator and over a sector of about 120.degree. (FIG. 1, pole pieces 1a and 1b), which presents a reduction of about 120.degree./180.degree., or 2/3, relative to the coupled flux in a single-phase motor of the same size. Hence this two-phase motor has a lower output as compared with a single-phase motor of the same size.